Polyimides are commonly employed in the semiconductor and packaging industry.
For instance, in the packaging of semiconductor chips, polyimide films are often coated onto substrates.
For instance, in the formation of multilayer substrates for mounting chips, one configuration employs an insulating substrate of a ceramic material onto which is deposited a pattern of metallic conductors. Usually, the conductors are three layers of metal being a layer of chromium, followed by a layer of copper, followed by an overlying layer of chromium. On top of the metallized ceramic substrate is placed a layer or film of a polyimide, and on top of the polyimide a second layer of a pattern of conductors is provided.
The metal contacting the polyimide on the second or subsequent layers can be, for instance, copper as disclosed in U.S. Pat. No. 4,386,116 to Nair, et al. and assigned to International Business Machines Corporation, the assignee of the present application, disclosure of which is incorporated herein by reference.
However, the adhesion between the copper and polyimide is not entirely satisfactory and could stand a degree of improvement. In particular, problems have occurred at the copper-polyimide interface resulting in lifting up of the copper line from the underlying polyimide substrate rendering the carrier unsuitable for its intended purpose.
Accordingly, in order that the configurations which involve a copper-polyimide interface be competitive in a commercial environment, it is necessary to improve the adhesion at the copper-polyimide interface.